1. Technical Field
The present invention relates generally to devices and methods for processing synchronization signals used to coordinate scanning in video devices and, more particularly, to a digital vertical sync separator that can separate a vertical synchronization signal from a high frequency and nonstandard input video signal.
2. Discussion
A typical video signal contains a composite synchronization signal that coordinates the horizontal and vertical sweeping action of an image scanning beam. The scanning beam generates a video image by drawing a series of horizontal lines starting at the top of the image in a left to right direction. When the video image has been completely generated by the scanning beam, the scanning beam returns to the upper left-hand corner of the image, and the scanning process is repeated. The horizontal and vertical sweeping action allows the video image be displayed in raster-like fashion on a screen or other viewing surface.
Embedded within the composite synchronization signal are horizontal and vertical synchronizing, or sync, pulses. These sync pulses occur, as the scanning beam is retraced, to effectively create horizontal and vertical blanking intervals. To properly blank the scanning beam, however, the vertical sync pulse must be separated from the horizontal sync pulse.
The separation of composite synchronization signals into their component parts has long been performed in the video arts using a variety of analog and digital methods and devices. Many of these methods are inflexible, in that they rely on particular timing characteristics of components used to effect the separation. Other methods process the composite synchronization signal by comparing an input sync signal with a reference signal having a known standard format. Such a methodology cannot reliably separate the composite synchronization signal into its component parts when the input signal is of a non-standard format. Still other sync separation methodologies cannot operate when the vertical sync frequency exceeds a certain value. For example, many sync separation devices cannot reliably separate a vertical sync signal when the frequency of the vertical sync signal is higher than 150 Hz. In addition, the circuitry required to implement these synch separation devices often requires numerous components and complicated circuit design.
Therefore, it is an object of the present invention to provide for a vertical sync separator utilizing a device-independent methodology that minimizes the size and complexity of the associated separator circuitry.
It is a further object of the present invention to provide an improved high-performance vertical sync separator which can reliably operate during high frequency and non-standard input signal conditions.
From the subsequent detailed description taken in conjunction with the accompanying drawings and subjoined claims, other objects and advantages of the present invention will become apparent to those skilled in the art.